1. Field of the Disclosure
The present disclosure relates generally to semiconductor devices and, more particularly, to laterally diffused metal oxide silicon (LDMOS) transistors.
2. Description of the Related Art
Laterally diffused metal-oxide-semiconductor (LDMOS) transistor devices frequently are used as power transistors in automotive applications and other high voltage/high current implementations due to their compatibility with many complementary MOS (CMOS) fabrication processes. LDMOS devices utilize a drift region between the channel region and the drain region. The PN junctions of the body and drift region can lead to a relatively low breakdown voltage (BVdss). A reduced surface field (RESURF) structure often is employed to deplete the drift region in both vertical and lateral directions, thereby reducing the electric field in the PN junctions surrounding the drift region and thus raising the breakdown voltage (BVdss) of the device. A LDMOS device also may employ a “double RESURF” structure, in which the drift region contains both n-type and p-type regions, and which provides for the depletion of the two regions and the reduction of the electric field in the related junction areas. Double RESURF structures typically apply the drain voltage to isolation regions in order to deplete both the n-type and p-type regions. LDMOS devices often utilize a buried isolation layer to achieve high-side configurations, and biasing the isolation regions at the drain voltage increases the field stress between the body of the LDMOS device and the buried isolation layer. Breakdown thus may instead occur between the body and the buried isolation layer, thereby limiting the breakdown voltage.